SEOUL —
North Korean leader Kim Jong Un said his country is united following a political purge that included the execution of his uncle. In a New Year's day speech, Kim also called for better relations with South Korea while warning Seoul and Washington that conflict on the peninsula could lead to a nuclear catastrophe.

North Korean leader Kim Jong Un spoke publicly for the first time Wednesday about a bloody purge in December of challengers to his political power.

In the high-level upheaval, Kim executed his uncle and one-time mentor, Jang Song Thaek, believed to be Pyongyang's number two in power.

South Korea's spy agency said at least two of Jang's followers were also killed as the young leader sought to consolidate his rule.

The unprecedented publicity of the violent removal of someone so close to the Kim family raised concerns about stability in the nuclear-armed North.

But in an annual New Year's Day speech aired by state broadcasters, Kim Jong Un said he removed what he called “factionalist filth” lurking in the party in order to restore unity.

He said the Korean Workers' Party detected and purged the anti-Party, counterrevolutionary factionalists at an opportune time and with a correct decision. He said the party and revolutionary ranks were further consolidated and their single-hearted unity was solidified by 100 times.

Jang Song Thaek was married to Kim Jong Un's aunt, Kim Kyong-hui, the younger sister of his father Kim Jong Il.

The aunt and uncle helped Kim Jong Un in the leadership transition after his father's sudden death two years ago. But uncle Jang was seen as a threat to the young Kim's power base as he sought to replace officials from his father's generation with younger loyalists.

Kim Jong Un is the world's youngest authoritarian ruler at about 30 years old.

While some of Jang's supporters were called back from overseas consulates, his wife, according to South Korean officials, was untouched by the purge.

In the speech, Kim Jong Un called for improved ties between Pyongyang and Seoul and an end to slander that harms both sides and efforts to one day reunify the peninsula.

He said they will join hands with anyone who opts to give priority to the nation and wishes for its reunification, regardless of his or her past, and continue to strive for better inter-Korean relations.

Korea was divided after World War II into a Soviet-influenced North and a United States-influenced South. Kim Jong Un's grandfather, Kim Il Sung, attempted to forcibly unify the peninsula under communism in a 1950 invasion that sparked the Korean War. The three years of fighting ended with an armistice leaving both sides, technically, in a continuous state of war.

Kim Jong Un said it was heartrending to see the peninsula divided by foreign forces, a reference to the 28,000 U.S. troops that are protecting South Korea from re-invasion.

He repeated rhetoric that U.S. and South Korean military exercises are preparation for a nuclear attack on the North and warned that accidents during the drills may lead to all-out war.

He said should another war break out on this land it will result in a deadly nuclear catastrophe and the United States will never be safe. He says all Korean people must not tolerate the maneuvers for war and confrontation by the bellicose forces at home and abroad, but stoutly resist and frustrate them.

South Korean officials said the political purge in North Korea revealed weakness in Kim Jong Un's leadership and warn he may attempt a military provocation in the coming months as a show of strength.